Fusion

Discussion on physics, models and calculation methods
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Jaakko Leppänen
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Re: Fusion

Post by Jaakko Leppänen » Tue Feb 26, 2019 10:44 am

Is that an error message that terminates the calculation, does it simply hang?
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M.K.
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Re: Fusion

Post by M.K. » Tue Feb 26, 2019 12:56 pm

It does not terminate it but I would like to know the possible reasons for it to appear, if it would have an impact on the calculation and if it is in general normal when using STL files. The STL files are water-tight.

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Re: Fusion

Post by Jaakko Leppänen » Wed Feb 27, 2019 2:15 pm

Serpent uses a ray-test to figure out whether the particle is inside or outside the STL solid. This ray test can fail if the ray hits too close to a boundary between two triangular facets. To overcome the problem, a new ray is started in another direction if the outcome is uncertain. This error is most likely related to a situation where the particle is very close the boundary between two facets, and the ray test fails multiple times in a row.

The result of the error is that the position cannot be determined, and the particle is put in the background universe instead. If these are rare events, then it should not have any effect on the results.

I would gladly take a closer look at the problem if you want to send me the input files...
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Re: Fusion

Post by M.K. » Thu Apr 04, 2019 12:33 pm

Dear Jaakko,

Thank you very much for replying so fast to my questions and willing to take a look at it! I found out that this issue arises when I rotate a sector by an arbitrary degree and saw in the forum that people encountered the same. When I try the full geomerty and exact positions I will be able to say if I would really need you to look at it. Before this I prefer to avoid bothering you with it.

In addition, NJOY does not work for me so I can not use it. For this reason I would like to ask for kind assistance in generating libraries for the polyethylene moderator and the radioactive source Pu-238 if possible.

Best Regards!

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Re: Fusion

Post by Jaakko Leppänen » Thu Apr 04, 2019 2:56 pm

Unfortunately we don't have thermal scattering data for polyethylene in our Serpent libraries, but you can use the data distributed with MCNP. Also the JEFF-3.2 data library available at the NEA Data Bank includes TSL data for polyethylene:

https://www.oecd-nea.org/dbforms/data/e ... s/jeff_32/

Click the download link under "Download Thermal Scattering Law data" (the list doesn't include polyethylene, but the file includes data for "poly", which I assume stands for polyethylene).

The radioactive decay data for Pu-238 is available in the standard decay data libraries.
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Re: Fusion

Post by M.K. » Thu Apr 04, 2019 3:39 pm

Kiitoksia oikein paljon! :)

I will see if I can make things work. If not I will turn to you for more questions.

Best Regards!

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Re: Fusion

Post by M.K. » Mon May 27, 2019 6:10 pm

Dear Jaakko,

Having included water as a moderator I discovered that for some reason I obtain zero for the neutron rate in the He3 detector.
It runs fine without it for thermal (se 0.025) as well as higher energy neutrons. The geometry does not seem to be the problem because everything is water-tight and to make sure I excluded it from the calculation leaving only the detector and the source.
This time I would like to use the opportunity and send you some files along with my script if you agree and have the time to go through it.

Best Regards!

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Re: Fusion

Post by Jaakko Leppänen » Mon Jun 03, 2019 11:34 am

Sure, send me the input files and I'll take a look.
- Jaakko

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Re: Fusion

Post by IlseHolanti » Mon Sep 30, 2019 1:05 pm

Hello. I have the same problem. Only in different cells different value :roll:
Last edited by IlseHolanti on Mon Sep 30, 2019 1:06 pm, edited 1 time in total.

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Re: Fusion

Post by IlseHolanti » Mon Sep 30, 2019 1:06 pm

IlseHolanti wrote:
Mon Sep 30, 2019 1:05 pm
Hello. I have the same problem. Only in different cells different value :roll:
Maybe there are other ways to solve the problem?

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